1. Field of the Invention
The invention relates to a web-fed rotary printing machine with at least one printing unit having at least one printing assembly which contains, arranged one above the other, a forme cylinder and an impression cylinder.
2. Description of the Related Art
DE 195 34 651 A1 shows a printing assembly for a rotary printing machine for indirect printing. Four printing-assembly cylinders are arranged one above the other, the journal mountings of which are capable of being clamped in jaws which are mounted moveably on side walls by means of slides. The cylinders are accessible on the end face through an orifice in the side wall after the jaws have been moved away. The cylinders can then be equipped with sleeves of different outside diameter. This design involves relatively complicated construction.
According to U.S. Pat. No. 6,085,650, printing-assembly cylinders are mounted in slides which are displaceable on columns. Here, in each case, two cylinders can be positioned in such a way that they cooperate in direct intaglio printing. The columns must have sturdy dimensioning in order to achieve high stability.
The brochure xe2x80x9cDicowebxe2x80x9d from MAN Roland Druckmaschinen AG, Augsburg, 2000, shows printing units of a web-fed rotary printing machine, in which printing-assembly cylinders of a double printing assembly for rubber-to-rubber offset printing are mounted on both sides in slides. The slides are displaceable on guides which are fastened in each case to opposite panels of an aperture in side walls.
The object of the invention is to provide a rotary printing machine for direct printing which arranges the printing-assembly cylinders in a space-saving way.
According to the invention, each printing unit includes a pair of side walls, and at least one double-printing assembly comprising two forme cylinders arranged one above the other, each forme cylinder being driven by its own drive motor, and at least one impression cylinder arranged between the forme cylinders so that a web can be printed between one of the impression cylinders and each of the forme cylinders, each cylinder having a pair of opposed ends. The mutual spacing between the impression cylinder and the forme cylinders can be adjusted by means of slides on which both ends of at least one of the forme cylinders and the impression cylinder are mounted, the slides being moveable on guide elements fastened to the side walls. By virtue of two forme cylinders being arranged on one or two impression cylinders, a compact printing unit with a plurality of printing positions is provided in a space-saving way.
Owing to the printing-assembly cylinders being mounted on the panels of the apertures in the side walls, a direct vertical introduction of the supporting forces for the printing-assembly cylinders into the side walls in their longitudinal direction takes place. The support therefore has high rigidity and low vibration, this being a precondition for a good print quality. High forces can be applied. The device is simple in structural terms and can consequently be set up cost-effectively. Thus, for example, the guide elements can be produced with commercially available straight guides. Printing can be carried out selectively by the intaglio printing or flexographic printing method on one and the same printing machine, and the machine can be changed over in a simple way from one method to the other. Also, both printing methods may be employed simultaneously. The printing machine manufacturer can produce the machines for both methods identically from the same components, thus making cost-effective manufacture possible. Moreover, the printing machines can be designed with a variable format, that is to say they can be converted in a simple way to different formats, that is to say different diameters of the forme cylinders and cut-off lengths. Furthermore, this printing machine can be changed over quickly to various production variants.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.